RE: Tire size on '90 325ic

["Fadeev, Alex" <alex.fadeev@xxxxxxxxxxx>]

Larry Schwarcz [mailto:lrs@domain.elided] wrote:
> 
> Well, it's time for me to buy some new front tires for my '90 325ic.  
> But, I've now been told by two different BMW places that I should 
> stick to the OEM size (195/65R14).  I now have 205/60R14s on the 
> rear since Yokahama didn't have the AVS Int in my size (yes, I really 
> like those AVS Intermediates!).

Larry,
205/60 is what's known as a +0 upgrade over stock 195/65 tires. It's a
perfectly safe and reasonable move, particularly since AVSi's are available
only in 205/60 size.

> Any thoughts on running a size that's not the OEM size?  I have a 
> program that shows differences between tires sizes that says:
> 
> Specification  Sidewall  Radius  Circumference  Revs/Mile Difference
> 195/65-14         127mm   305mm         1914mm      841     0.0%
> 205/60-14         123mm   301mm         1890mm      852    -1.2%
> 
> This shows that there wouldn't be much speedo error (-1.2%) and the
> new tire is 8mm (0.31") shorter and 10mm wider (0.39").

Other than your speedometer indicating slightly (1.2%) higher than actual
speed, there are no negatives to going with 205/60/14 tires. Since BMW only
guarantees it's speedometers to display 0-10% higher than actual speed, you
would effectively we moving that margin of error window to 1.2%-11.2% over
actual.

> So, it seems to me that the differences are very small in terms of
> how the car would handle.  But, are BMWs more sensitive to tire size
> differences than other makes?

Nope. I wore off two sets of 205/60 AVSi's on my E30 before retiring the car
into daily driver duty (SH30's from now on). AVSi's are the best dry non-R
tires you can put on stock E30 wheels!

alex f

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